title: Inositol hexakisphosphate-dependent processing of Clostridium sordellii lethal toxin and Clostridium novyi alpha-toxin.
abstract: Clostridium sordellii lethal toxin and Clostridium novyi α-toxin, which are virulence factors involved in the toxic shock and gas gangrene syndromes, are members of the family of clostridial glucosylating toxins. The toxins inactivate Rho/Ras proteins by glucosylation or attachment of GlcNAc (α-toxin). Here, we studied the activation of the autoproteolytic processing of the toxins by inositol hexakisphosphate (InsP(6)) and compared it with the processing of Clostridium difficile toxin B. In the presence of low concentrations of InsP(6) (<1 μM), toxin fragments consisting of the N-terminal glucosyltransferase (or GlcNAc-transferase) domains and the cysteine protease domains (CPDs) of C. sordellii lethal toxin, C. novyi α-toxin, and C. difficile toxin B were autocatalytically processed. The cleavage sites of lethal toxin (Leu-543) and α-toxin (Leu-548) and the catalytic cysteine residues (Cys-698 of lethal toxin and Cys-707 of α-toxin) were identified. Affinity of the CPDs for binding InsP(6) was determined by isothermal titration calorimetry. In contrast to full-length toxin B and α-toxin, autocatalytic cleavage and InsP(6) binding of full-length lethal toxin depended on low pH (pH 5) conditions. The data indicate that C. sordellii lethal toxin and C. novyi α-toxin are InsP(6)-dependently processed. However, full-length lethal toxin, but not its short toxin fragments consisting of the glucosyltransferase domain and the CPD, requires a pH-sensitive conformational change to allow binding of InsP(6) and subsequent processing of the toxin.
authors.affiliation: Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Guttenberg
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Papatheodorou
authors.forename: Selda
authors.initials: S
authors.lastname: Genisyuerek
authors.forename: Wei
authors.initials: W
authors.lastname: Lü
authors.forename: Thomas
authors.initials: T
authors.lastname: Jank
authors.forename: Oliver
authors.initials: O
authors.lastname: Einsle
authors.forename: Klaus
authors.initials: K
authors.lastname: Aktories
mesh_terms: D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000737:chemistry / Q000378:metabolism*; D003013:Clostridium / Q000737:chemistry*; D047989:Paraclostridium sordellii / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010446:Peptide Fragments / Q000494:pharmacology; D010833:Phytic Acid / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D010446:Peptide Fragments; C031815:toxB protein, Clostridium difficile; D010833:Phytic Acid